TW200533765A - Bake-hardenable cold rolled steel sheet having excellent formability, and method of manufacturing the same - Google Patents

Abstract

A bake-hardenable cold rolled steel sheet, and a method of manufacturing the same, designed to have bake hardenability and excellent formability suitable for automobile bodies, and the like. The steel sheet comprises 0.003~0.005% C, 0.003~0.03% S, 0.01~0.1% Al, 0.02% or less N, 0.2% or less P, 0.03~0.2% Mn and/or 0.005~0.2% Cu, and the balance of Fe and other unavoidable impurities in terms of weight%. When it comprises one of Mn and Cu, the composition of Mn, Cu, and S satisfies one of relationships: 0.58*Mn/S≤10 and 1≤0.5*Cu/S≤10. When it comprises both Mn and Cu, the composition satisfies the relationships: Mn+Cu≤0.3 and 2≤0.5*(Mn+Cu)/S≤20. MnS, CuS, and (Mn, Cu)S precipitates have an average size of 0.2 um or less. The steel sheets allow the content of solid solution to be controlled by fine MnS, CuS, (Mn, Cu)S precipitates, providing improved bake hardenability, formability, yield strength, and yield strength-ductility balance.

Description

200533765 IX. Description of the invention: [Technical field to which the invention belongs] TECHNICAL FIELD The present invention relates to cold-rolled steel plates used in automobile bodies and the like. More specifically, the present invention relates to a cold-rolled steel sheet that can be roast-hardened to improve the hardenability and formability by controlling the solid solution carbon content in the crystalline particles with a fine sinker, and a method for manufacturing the same. .

[Previously Fresh; J is King Technology 10] For materials used for automotive exterior panels, bake-hardened cold-rolled steel sheets are generally used to improve impact resistance. Bake-hardened cold-rolled steel sheets have excellent ductility through press forming, and have increased yield strength after baking or coating after press forming. That is, carbon or nitrogen is present as a void element in the solid solution of the steel and is trimmed for dislocations generated during press forming. Therefore, the yield point of the 15-bake-hardened cold-rolled steel sheet is increased. Baking hardened cold-rolled steel plates include clean aluminum steel (which is a batch-annealed material), and very low carbon nitrogen steel (IF steel). In the case of aluminum-killed steel, it is a batch-annealed material. A small amount of solid solution carbon remains in the steel and ensures aging resistance. At the same time, 20 to 10 is provided after baking treatment. MPa grade can be roasted and hardened. However, for these batch-annealed materials, there is a disadvantage of a lower increase in yield strength, even after baking, and lower productivity. In the case of extremely low carbon nitrogen steel, when solid solution carbon or nitrogen in the steel is completely precipitated by adding titanium or niobium to the steel, the formability of the steel is promoted. Baking hard 200533765 The extremely low carbon nitrogen steel is made by making the extremely low carbon nitrogen steel available for baking hardening. For bake-hardened extremely low carbon nitrogen steel, the hardenability can be ensured by controlling the amount of titanium or niobium and the amount of carbon to keep an appropriate amount of carbon in the steel. However, in the case of baking hardened very low carbon nitrogen steel, in order to keep 5 equivalents of carbon in the solid solution in the steel, it is necessary to add sulfur and nitrogen that will react with titanium or niobium and produce its precipitate. Control the amount of carbon, titanium or niobium in a very narrow range. Therefore, it is difficult to secure a high-quality product, and the manufacturing cost increases. L Ming Nai 3 10 Disclosure of content and technical problems Therefore, the present invention is based on the above problems, and the object of the present invention is to provide a bake-hardenable cold-rolled steel sheet, which does not add Ti and Nb and has high plasticity. Anisotropy index and lower in-plane anisotropy index, while improving baking hardenability and formability, and its manufacturing method. Technical Solution According to one aspect of the present invention, the above and other objects can be accomplished by providing a bake-hardenable cold-rolled steel sheet, which includes: 0.003 to 0.005% C; 0.003 to 0.03% S 0.01 ~ 〇 · 1% of A1; 0.02% or less of N; 〇 · 2% or less of ρ; 〇 · 〇3 ~ 0.2. /. At least one of Mn and 0.005 to 0.2% Cu; and the balance of Fe and other unavoidable impurities, which are weight. /. When the steel sheet contains one of Mn and Cu, the composition of Mn, Cu, and S satisfies one of the following relationships: 0.58 * Mn / S ^ 10 and 1 $ 0.5 * Cu / S $ 10 (in By weight), and when the steel sheet contains both Mn and Cii, the composition of 200533765 Mn, Cu, and S satisfies the relational expressions: Mn + Cu $ 〇3 and 2 $ 〇.5 * (Mn + Cu) / S $ 20 (by weight), and wherein the precipitates of MnS, CuS, and (Mn, Cu) S have an average size of 0.21 m or less. The cold-dried steel sheet according to the present invention can be classified into three types according to Tim 5 plus vanillin selected from the group consisting of Mn and Cu. That is, (1) a steel to which only Mη is added (Cii is excluded, which is also referred to as MnS sinking steel "), (2) a steel to which only cu is added (Mη is excluded, which is also referred to as" CuS precipitated steel, " , And steels with added Mη and Cu (which are also called MnCu Shendian steels), which will be described in detail below. (1) MnS precipitated steels include: 0 003 ~ 0.005% C; 0.005 ~ 10 〇 · 03% of s; 0.001 to 0.1% of A; 0.02% or less of N; 0.2% or less of P; 0.05 to 0.2% of Mn; and the balance of Fe and other inevitable Impurities are based on weight%, where the composition of Mη and S satisfies the relationship: 0.58 * Mn / SS 10 (by weight), and the Shen Dianwu of MnS has a size of 0.2 μm or less. The method for manufacturing MnS precipitated steel includes step 15: providing a hot-dried steel sheet by finishing rolling at a transition temperature of Ar3 or higher, and heating the steel sheet to 1,100 ° C or more After multiple temperatures, the steel sheet contains: 0.003 to 0.005% C; 0.005 to 0.03% S; 0.01 to 0.1% A1; 0.02% or less N; 0.2% or less p; 〇 〇5 ~ 〇2% of Mn; and The balance of Fe and other unavoidable impurities is 20% by weight. Among them, the composition of Mη and S satisfies the relational formula: 0.58 * Mη / SS10, which is based on weight; at 200 ° C / The hot-rolled steel sheet is cooled at a cold part rate of one minute or more; the cooled steel sheet is wound at 700 ° C or less; the steel sheet is cold-rolled; and the cold-rolled steel sheet is continuously annealed. (2) CuS precipitated steel contains: 0.003 ~ 0.005% C; 0.003 ~ 200533765 0.025% S; 0.01 ~ 0.08% Al; 0.02% or less n; 0.2% or less P; 0.01 ~ 0.2% Cu; and the balance of Fe and other unavoidable impurities are based on wt%, of which the composition of Cu and S meets the

Formula: 1 $ 0.5 * Cu / S $ 10, which is based on weight, and wherein the precipitate of cuS 5 has an average size of 0.1 μm or less. The method for manufacturing a CuS-excited steel comprises the steps of: hot rolling a steel sheet to provide a hot-rolled steel sheet by finishing rolling at a transformation temperature of Ah or higher, and the steel sheet is heated again to 1,100. After a temperature of 〇 or higher, the steel sheet contains 0.003 to 0.005% C; 0.003 to 0.025% S; 0.01 to 0.08% A1; 0.02% or less N; 0.2% 10 or less P 0.01 ~ 〇 · 2% of Cu; and the balance of Fe and other unavoidable impurities, which are based on weight%, wherein the composition of Cu and S satisfies the relationship: 1 $ 〇.5 * Cu / SS 10, which is based on weight; cooling hot-rolled steel sheet at a cooling rate of 300 ° C / min or more; coiling the cooled steel sheet at a temperature of 700 ° C or less; cold-rolling the steel sheet; and cold-rolling The steel sheet is continuously annealed. 15 (3) MnCu precipitated steel contains: 0.003 to 0.005% of C; 0.003 to 0.025% of S; 0.01 to 0.08% of A1; 〇_〇2% or less of N; 0.2% or less of 〇; 〇3 ～ 〇 · 2% of Mn; 0.005 ~ 0_2% of Cu; and the balance of Fe and other impurities that are not avoided, which are based on weight%, of which Mn, Cu, and S, The composition satisfies the relationship: Mn + Cu $ 0.3 and 2 $ 200.5. * (Mn + Ci0 / S $ 2〇, which is based on weight, and among which, MnS, CuS, and (Mn, Cu) S are splashed The material has an average size of 0 · 2 um or less. The method of manufacturing MnCu precipitated steel includes the steps of: providing the hot-rolled steel plate at the transformation temperature of Ar3 or higher by hot-rolled steel plate, which is heated again After reaching a temperature of 1,100 ° C or higher, the steel sheet contains: 〇 · ⑽3 ~ 〇 · ⑻5% C 200533765; 0.003 ~ 0.025% S; 0.0001 ~ 〇08% Al; 0 · 02 % Or less N; 0.2 ° / 〇 or less P; 0.03 to 0.2% Mn; 0.005 to 0.22 Cu; and the balance of Fe and others Avoided impurities are based on weight 0 / 〇, where Mn, Cu and S satisfy the relationship: Mn + Cu ^ O .3 and 2 $ 5 0.5 * (Mn + Cu) / SS20 by weight; cooling hot-rolled steel sheet at a cooling rate of 300 ° C / min; coiling cooling steel sheet at 700 ° C or less; Cold rolling a steel sheet; and continuously annealing a cold rolled steel sheet. The above-mentioned bake-hardenable cold rolled steel sheet of the present invention can be applied to a ductile cold rolled steel sheet having a tensile strength of 240 MPa, or a grade of 340 MPa 10 or More high-strength cold-rolled steel sheet with more tensile strength. In the case of ductile cold-rolled steel sheet at 240 PMa level, the steel sheet contains 0.003 to 0.005% C, 0.003 to 0.03% S; 0.01 to 0.1% A1; 0.004 % Or less of N; 0.015% or less of P; 0.03 ~ 0.2% of Mn and at least 0.005 ~ 0.2% of Cu; and the balance of Fe and other inevitable impurities, which are In terms of% by weight, when the steel sheet contains one of Mn and Cu, the composition of Mn, Cu, and S satisfies one of the following relations: 0.58 * Mn / S $ 10 and 1 $ 0.5 * Cu / SS10, It is based on weight, and when the steel plate contains both Mη and Cu, the composition of Mn, Cu, and S satisfies the relationship: Mn + CuS0.3 and 2 $ 0.5 * (Mn + Cu) / S $ 20, which is based on Weight 20 And wherein the precipitates of MnS, CuS and (Mn, Cu) S have an average size of 0.2 um or less. In the case of 340 MPa or more high-strength cold-rolled steel plates, they can be classified into steels containing at least one of P, Si, and Cr (as a solid solution strengthening agent) and N containing more south ( Precipitation strengthening agent). That is, P is 0.2% or less than 200533765, 0.1 to 0.8 ° /. Of Si, and 0.2 ~ 1.2. At least one of Cr is contained in the ductile cold-rolled steel sheet. If only p is added to the ductile cold-rolled steel sheet, the content of P is preferably in the range of from 0.3 to 0.2%. In addition, the 'high-strength property can be ensured by increasing the N content to 0.005 to 0.02% and adding an A1N precipitate of P of 50.03 to 0.06 ° / 0. In order to further promote the formability of the cold-rolled steel sheet, the steel sheet may further include 0.01 to 0.2% Mo. The beneficial effect is obvious from the above description. According to the present invention, the bake-hardenable 10 cold-rolled steel sheet can control the solid solution content in the crystal grains by the fine MnS, CuS, (Mn, Cu) S precipitates. Therefore, it provides improved baking hardenability, formability, yield strength, and yield strength-ductility balance. The above-mentioned and other objects, features and other advantages of the present invention will be clearly understood from the following detailed description in conjunction with the accompanying drawings, in which: Figures la to lc show the solid solution carbon content in the crystalline particles and Shen Dian A graphical representation of the relationship between physical dimensions, where Figure la shows the situation of MnS precipitated steel, Figure lb shows the situation of CuS precipitated steel, and Figure lc shows the situation of MnCu Shen Dian steel; 20 Figures 2a and 2b The graph is a graph showing the relationship between the size of MnS precipitates and the cooling rate, wherein FIG. 2a shows the case of 0.58 * Mn / S < 10, and FIG. 2b shows 0.58 * Mn / S > Case 10; 苐 3a to 3c are diagrams showing the relationship between the size and cooling rate of CuS precipitates, where Fig. 3a shows the case of 0.5 * Cu / S = 2.56, and Fig. 10 200533765 3b shows 0.5 * Cu / S = 8 · 1, and Figure 3c shows the case of 0.5 * Cu / S = 28; and

Figures 4a and 4b are diagrams showing the relationship between the size and cooling rate of MnS, CuS, and (Mn, Cu) S precipitates. Among them, Figure 4a shows 2 $ 5 0. 5 * (Mn + Cu) / The case of S $ 20, and Fig. 4b shows the case of 0.5 * (Mn + Cu) / S > 20. I: Embodiment 3 Best Mode A preferred embodiment of the present invention will now be described in detail. However, it should be noted that the present invention is not limited to these embodiments. For the composition of the steel sheet of the present invention, "weight./〇" will be simply expressed as "%," thereafter. The inventor of the present invention has discovered that the addition of Ti & Nb to promote bake hardenability through research has been described below The new fact is that the solid solution carbon content in the crystalline particles is appropriately controlled by the fine precipitates of MnS, CuS or (Mn, Cu) S, thereby increasing the yield strength, especially the post-baking yield strength. These precipitates have positive effects on the increase in yield strength, plastic anisotropy index, and in-plane anisotropy index caused by precipitation strengthening. Refer to Figures 1a to 1c for MnS, CuS, and (Mn, Cu) The finer the distribution of the S precipitate, the greater the decrease in the solid solution carbon content in the crystalline particles by 20. This helps the relatively free movement of the solid solution carbon remaining in the crystalline particles. More specifically, the solid solution carbon It can be removed freely in the crystal grains, and easily coupled to a movable dislocation, thereby affecting the aging characteristics at room temperature. The solid solution group stone can also be moved to a more stable area, such as the grain boundary or near the Shen Dianwu , Separated in these areas, And at a high temperature (for example, during baking), it is activated in 200533765 to make the shirt ring hardenable. Therefore, the reduction of the solid solution carbon content in the crystalline particles means that carbon exists in more stable areas, such as The particle boundary or the vicinity of the fine Shendian, and affect the baking hardenability. Figures 1a to 1c are diagrams showing the relationship between the size of solid solution carbon in the crystalline particles and the size of the precipitates. In the figure, the figure shows情况 In the case of Shen Dian's steel, Figure lb shows the situation of CuS Shen Dian's steel, and Figure ^ shows the situation of MnCu precipitated steel. The finer the size of the precipitate, the greater the reduction in the solid solution carbon content in the crystalline particles. And for the carbon that does not exist in the crystalline particles between the total carbon amount, it effectively affects the bake hardenability. With reference to Figures ^ to 10, it can be seen that when the MnS precipitate has about 0.2 um * less Size (Fig. 1a), when the CuS precipitate has a size of about 0 1 _ or less (Figure 1b) 'and when] \ 4nCu Shen Dianwu has a size of about 0.2 um or less (No. In the lc chart, the carbon content of the solid solution in the crystalline particles is reduced to about Shantou or less. Therefore, in order to ensure the effective carbon content for baking hardenability, it is important to finely distribute the MnS, CuS, or MnCu sinks while keeping the total carbon content within the range of 0.003 to 0.005% in the steel. A method for finely distributing these Shen Dian objects was studied, and the results indicate that the fine distribution of these Shen Dian objects in the crystalline particles can be controlled by controlling the content of Mn, Cu and S and the composition of these elements in steel, and controlling The cooling rate after hot rolling is achieved. 20 Figure 2a is a diagram obtained after studying the size of the precipitate based on the cooling rate after hot rolling of the steel plate, this steel plate contains: 0.004% C; 0.15% Mn; 0.008% P; 0.015% S; 0.03% A1; and 0.0012% N (where 0.58 * Mn / S = 5.8). Referring to Fig. 2a, by controlling the cooling rate of the steel plate under the condition that the mixture of Mη and S satisfies the relationship of 0.58 * Mn / SS10, the MnS precipitate has a size of 0.2um or less. Figure 3a is a diagram obtained after studying the size of the precipitate based on the cooling rate after hot rolling of the steel plate. This steel contains: 0.004% C; 0.001% P; 0.008% S; 0.05% A1; 0.0014% N; and 0.041% 5 Cu (where 0.5 * Cu / S = 2.56). Referring to FIG. 3a, since the mixture of Cu and S satisfies the relationship: 0.5 * Cu / SS10, the cooling rate of the steel plate is controlled, and the CuS precipitate has a size of 0.1 μm or less. Figure 4a is a diagram obtained after studying the size of the precipitate according to the cooling rate after cold rolling of the steel sheet. The steel contains: 0.004% C; 0.13% Mn; 10 0.009% P; 0.015% S; 0.04% A1; 0.0029% N; and 0.04% Cu (where Mn + Cu = 0.17% and 0.5 * (Mn + Cu) / S = 5.67). Referring to Figure 4a, by satisfying the relationship due to the mixture of Mn, Cu, and S: 2 S 0.5 * (Mn + Cu) / SS 20 to control the cooling rate of the steel plate, MnS, CuS, (Mn, Cu) S Shen Dianwu It has a size of 0.2 uni or less. 15 The bake-hardenable cold-rolled steel sheet according to the present invention has high yield strength, and therefore, can reduce the thickness of the steel sheet. Therefore, 'the cold-rolled steel sheet according to the present invention has the effect of reducing the weight of its product. Furthermore, the low in-plane anisotropy of the cold-rolled steel sheet of the present invention minimizes the formation of enemy lines or ears during or after the guarding process of the steel sheet. The cold-rolled steel sheet of the present invention is also promoted by the presence of appropriate carbon content in the grain boundary due to the fine grains; the grain boundary is used to avoid brittleness caused by the weakening of the grain boundary after processing.化 断。 Destruction. And its manufacturing method will be described in detail under the present invention's bake-hardenable cold-rolled steel sheet. 13 200533765 [Cold-rolled steel sheet of the present invention] Stone counter (C) · 〇〇〇3 ~ 〇. 05% Although the solid solution in the crystal grains is reduced, but because the carbon sinks into the fine particles of the fine particles, Baking hard and pure is increased without loss of room temperature when the tr is separated, or slightly sinking; _ = around the object = inside = increasing grain boundaries or fine Shen Dian 10 baking is more modified [ie, to ensure that you can bake Hardenability, carbon content exceeds% and 0.00031 / 0 or more. However, if the carbon content exceeds 0.05%, the formability will rapidly decrease. Therefore, the carbon content is preferably in the range of 0.003 to 0.005%. Sulfur (S): 0.003 to 0.003% Sulfur content less than 0.003% not only reduces the amount of Mns, CuS, and (Mn, Cu) 15 sinking and killing, but also produces excessively coarse precipitates, so reducing the Baking hardening. More than 0.03 ° /. The sulfur content will cause a large amount of solid solution sulfur. Therefore, the ductility and formability of the steel sheet are significantly reduced, and the possibility of hot cracking is increased. According to the present invention, for MnS precipitated steel, the sulfur content is preferably in the range of 0.005 to 0.03%, and for CuS precipitated steel, the sulfur content 20 is preferably in the range of 0.003 to 0.025%. For MnCu precipitated steel, the sulfur content is preferably in the range of 0.003 to 0.025%. Aluminum (A1): 0.01 to 0.1% Aluminum is commonly used as a deoxidizing element. However, in the present invention, aluminum is added to the steel to precipitate nitrogen in the steel, and thus the formability is avoided 14 200533765 due to the decrease in solid solution nitrogen. An aluminum content of less than 0.01% results in an increase in the solid solution nitrogen content, which reduces the formability, and an aluminum content of more than 0.1% causes an increase in the solid solution aluminum content, thereby reducing the ductility of the steel. According to the present invention, the content of CuS precipitated steel and MnCu Shendian steel is preferably in the range of 0 to 50.08%. If the nitrogen content is increased to 0.005 ~ 0.02%, high-strength steel plates can be obtained by the strengthening effect of A1N Shen Dianwu. Nitrogen (N): 0.02% or less An unavoidable element that is introduced into the steel during the manufacturing method of the nitrogen-based steel, and in order to obtain strengthening effect, it is preferable to add 10 to the steel in an amount not exceeding 0. In order to obtain a ductile steel sheet, the nitrogen content is preferably 0004% or less. In order to obtain a high-strength steel sheet, the nitrogen content is preferably 0.005 to 0.02%. Although the nitrogen content 1 needs to be 0.005% or more in order to obtain a strengthening effect, a nitrogen content of more than 0.02% causes deterioration of the formability of the steel sheet. For steels that provide high strength using nitrogen, the dish content is preferably 0.03 to 0.06%. According to the present invention, in order to ensure high strength by the A1N precipitate, the combination of A1 and N, that is, 0.52 * A1 / N (where A1 and N are expressed by weight%) is preferably in the range of 5. Combinations of A1 less than 1 (0.552 * A1 / N) will result in reduced formability due to solid solution nitrogen, while combinations of A1 & N more than 5 (〇 · 52 * Α1 / N) cause negligible Strengthen the effect. 20 Phosphorus (P): 0.2% or less Phosphorus is a mixed element, which will increase the solid solution strengthening effect while reducing the r-value (plasticity-anisotropy index) slightly, and can ensure that Shen Dianwu is controlled. Steel strength. Therefore, in order to ensure high strength by controlling the P content, the P content is preferably 0.2% or less. A phosphorus content of more than 0.2% will cause the ductility of the steel sheet to decrease. When phosphorus is added to the steel alone to ensure high strength of the steel plate, the P content is preferably from 0.03 to 0.2%. For ductile steel sheets, the p content is preferably 0.015% or less. For steel sheets in which high strength is ensured by using α1ν precipitates, the P content is preferably 0.03 to 0.06%. This is because although the target strength is ensured by a phosphorus content of 5.03% or more, a phosphorus content of more than 0.006% will reduce the ductility and formability of the steel. According to the present invention, in the case where the high strength of the steel sheet is ensured by addition and &, the ρ content can be appropriately controlled to 0.2% by weight or less in order to obtain the target strength. In this case, even if the P content is 0.015% or less, high strength can be ensured. In the present invention, at least one of Mg and Cu is preferably added to steel. These elements are mixed with sulfur and generate MnS, Cu ^ (Mn, Cu) s Shen Dianwu. Manganese (Μη): 0.03 ~ 0.2% Manganese is an admixture element, which is used to precipitate solid solution 15 body sulfur in steel with MnS precipitate, thus avoiding thermal cracking caused by solid solution sulfur. In the present invention, Mn is precipitated as fine MnS and / or (Mn, Cu) S precipitates under conditions where S and / or Cu is mixed with Mn and the cooling rate is appropriate. Fine deposits can impart bake hardenability to the steel sheet during baking treatment by causing carbon separation due to particle boundaries or around the precipitate, rather than crystalline particles. To achieve these 20 effects, the amount of Mn $ needs to be 0.03% or more. At the same time, the manganese content of more than 0.2% of rhenium caused coarse precipitates due to the high manganese content, thus deteriorating the hardenability of the steel sheet. If Mη is added to the steel alone (excluding Cu), the manganese content is preferably 0.05 to 0.2%. Steel (Cu): 0.005 ~ 0.2% 16 200533765 Copper is an admixture element, and its cooling rate under the appropriate conditions for s and / or "11 and (: 11 mixture and coiling treatment before hot rolling treatment) Produces fine precipitates. Fine precipitates impart bake hardenability to 5 steel plates during baking treatment by causing the steel to be separated at the grain boundaries or around the sink (rather than crystalline particles). To achieve these effects, Cu The content needs to be 0.005 0/0 or more. At the same time, the copper content of more than 0.2% causes coarse precipitates due to the higher copper content, thus deteriorating the hardenability of the steel sheet. If cu is added to the steel alone ( Excluding Mη), the copper content is preferably 0.01 to 02%. According to the present invention, the content and mixing of Mn, Cu, and S are controlled to produce 10 fine precipitates, and these are based on the amount of Mη and / or Cii For steel precipitated by MnS, the mixture of Mη and S is preferably a full-stop relationship: 0.58 * Mn / SS10 (where Mη and S are expressed by weight%). Mη is mixed with S to produce a MnS precipitate. MnS Precipitate can change the precipitation state according to the amount of Mn and S added, and Therefore, it affects the bake hardenability, yield strength of 15 degrees, and the in-plane anisotropy index. A value of 0.58 * Mn / S greater than 10 produces coarse MnS precipitates, resulting in bake-hardenability and in-plane anisotropy. Anisotropy index worsens 0 For CuS sinking steel, the mixture of Cu and S preferably satisfies the relational formula: $ 0.5 * Cu / SS10 (wherein, and 3 are expressed by weight%). CuS mixed with S produces CuS precipitation It can change the precipitation state according to the amount of cu and S added. Therefore, it affects the bake hardenability, plasticity-anisotropy index, and in-plane anisotropy index. 1 or more of 0.5 * Cu / S value can produce effective CuS precipitates, and greater than 0.5 × * Cu / S values produce coarse CuS precipitates, resulting in bake hardenability, plasticity-anisotropy index, and in-plane anisotropy17 200533765 The deterioration of the property index. In order to securely ensure that CuS sinkers with 0.1 μm or less, the value of 0.5 * Cu / S is preferably 1 to 3. When Mn and Cu are added to the steel plate together, Mn and Cii The total amount is preferably 0.3 ° / 0 or less. This is due to the fact that the total Mη and Cu content of more than 0.3% may produce coarse precipitates, so Detract from baking hardenability. The value of 0.5 * (Mn + Cu) / S (where Mn, Cu and S are expressed by weight%) is preferably 2 to 20. Mn and Cu are mixed with S to produce MnS and CuS. And (Mn, Cu) S precipitates, which can change the precipitation state according to the amount of Mn, Cu, and S added, and affect the bake hardenability, plasticity-anisotropy index, and in-plane anisotropy 10 index. 2 Or more 0.5 * (Mn + Cu) / S value can produce effective Shen Dianwu, and more than 0.5 ** (Mn + Cu) / S value of 20 produces coarse precipitates, resulting in bake hardenability, plasticity-each The anisotropy index and in-plane anisotropy index deteriorated. According to the present invention ', with a value of 0.5 * (Mn + Cu) / S in the range of 2 to 20, the average size of Shen Dianwu is reduced to 0.2 um or less. In this case, the precipitate (number / mm 2) having an area of 2 × 106 or more per 15 bits is distributed in the particles desirably. When the value is lower than or higher than 7 as 0.5 * (Mn + Cu) / S, the type and number of Shen Dianwu changes significantly. In particular, when the value of 0.5 * (Mn + Cu) / S is 7 or less, many extremely fine individual precipitates of MnS and CuS are uniformly distributed, instead of (Mn, Cu) S being mixed with Shen Dianwu. At the same time, when the value of 0.5 * (] y [n + Cu) / S is more than 20, the number of precipitates distributed in the particles is reduced, regardless of the small difference in size of the precipitates, because (Mn, Cu) The amount of S-complex precipitates increased. In the present invention, an increase in the number of precipitates can promote bake hardenability, in-plane anisotropy index, resistance to embrittlement of secondary operations, and the like. For this reason, it is preferable that the area per unit area is 2 X 108 or more; the objects (number / mm2) are distributed on the grain and grain boundaries. In the present invention, even if the value of 0.5 * (Mn + Cu) / S is the same, the smaller the added amount of Mn and Cu can reduce the number of distributed precipitates. If Mη and Cu content increase, the Shen Dianwu becomes coarse, resulting in a decrease in the number of distributed Shen Dianwu. According to the present invention, the MnS, CuS, and (Mn, Cu) S precipitates preferably have an average size of 0.2 µm or less. MnS, CuS & (Mn, Cu) s precipitates can have different appropriate sizes depending on the amount of Mn and Cu added. Optimally, the precipitate has a size of 0.2 μm or less for the Mn precipitate system, a size of 0.2 μm or less for the CuS sinker, and for the Mns, CuS, and (Mn, Cu) S sinkers. ; The mixture of temple objects is 10 inches with a ruler of 0.2 um or less. According to the present invention, if the MnS, CuS, and (Mn, Cu) S precipitates have an average size larger than their preferred sizes, the bake hardenability is particularly deteriorated, and the plasticity-anisotropy index and in-plane anisotropy are deteriorated. index. When the size of the sinker is reduced ', it is preferable in terms of baking hardenability. At the same time, according to the present invention, for the application of 340 MPa grade or more high-strength 15-degree steel plates, at least one of the solid solution strengthening elements (g 、, p, Si and up to: >,) can be added to Steel plate. Because the effect obtained by adding a disc is already described, its description will be omitted. Silicon (Si): 0.1 ~ 〇 8%

Si system-a kind of blending element, which can increase the solid solution strengthening effect. Although 20 lowers the ductility slightly, it ensures the high strength of the steel plate. Meanwhile, Shen Dian system is controlled according to the present invention. A content of 01% or more can ensure the strength of the steel sheet, but a content of more than 0.8% will cause a reduction in ductility. Chromium (Cr): 0.2 to 12%

Cr series-a kind of blending element, which increases the solid solution strengthening effect, and at the same time promotes the aging resistance of 19 200533765 at room temperature. Therefore, to ensure the high strength of the steel plate, although the in-plane anisotropy index of the steel plate is reduced. The system is controlled according to the present invention. Chromium content of 0.2% or more can provide strength to the steel sheet, but chromium content of more than 1.2% will cause its ductility to decrease. 5 Molybdenum (Mo) can be added to the cold-rolled steel sheet of the present invention. Molybdenum: 0.01 to 0.2%

The Mo-based species joins vanillin, which increases the plasticity and anisotropy index of the steel sheet by 0.01 /. On the other hand, the content will increase the plastic-anisotropy index, but it exceeds 0.2 /. The indium containing s causes thermal cracking and no additional improvement in plasticity. Anisotropy index 10. [Method for manufacturing cold-rolled steel sheet] A special feature of this month is that the steel sheet that satisfies the above-mentioned composition can be processed by hot rolling and cold rolling to have a slight reduction in average size. The average size of the precipitate is affected by the content and composition of Mn and cl ^ s and the manufacturing method I5, and the land preparation is directly affected by the cooling rate after hot rolling. [Hot rolling conditions] According to the present invention, the steel satisfying the above composition is reheated, and thereafter hot rolling is performed. The reheating temperature is preferably 1,100 ° C or more. This is attributed to the coarse Shen Dianwu being reheated at a temperature lower than uoot, which was generated during the last 20 scales and maintained in an incompletely dissolved state. Therefore, the coarse Shenlin was retained even after hot rolling. It is a good idea that hot rolling is performed on the cylinders that are implemented when finishing rolling at a temperature of Baqiao transformation or more. If finish rolling is carried out below the An transition temperature, rolling debris is generated and the ductility and formability of the steel sheet are significantly reduced. 20 200533765 The cooling rate after hot rolling is preferably 200 ° C / min or more. More specifically, the cooling rates of (1) MnS Shendian steel, (2) CuS precipitated steel, and (3) MnCu precipitated steel are slightly different. First, the cooling rate of steel precipitated in MnS is preferably 200 ° C / min 5 or more. Even when the composition of Mn & S satisfies the relationship according to the present invention: 0.58 * Mn / S $ 10, a cooling rate below 200 ° C / min will produce a coarse MnS sinker with a size greater than 0.2 um. That is, as the cooling rate increases, several nuclei are generated, and thus the MnS precipitate becomes finer. When the composition of S has a relational formula: 0.58 * Mn / S > 10, the number of coarse precipitates in an incompletely dissolved state during the reheating treatment period 10 increases, so that even if the cooling rate is increased, the number of cores is not Increased, therefore, MnS Shen Dianwu will not become thinner (Figure 2b, 0.0038%; 0.003%; 0.011%; 0.009 〇 / 0; 0.035% A1; and 0.0043% N). Referring to Figures 2a and 2b, the increase in cooling rate results in a finer 15 MnS sinker, so there is no need to provide an upper limit for the cooling rate. However, even when the cooling rate is 1,000 ° C / min or more, the MnS precipitate has not been further reduced in size, and therefore, the cooling rate is more preferably in the range of 200 to 1,000 ° C / min. Secondly, in the case of CuS-precipitated steel ', the cooling rate after hot rolling is 300 to 300. (3 / minute or more. Even when the composition of Cu and S satisfies the relational formula according to the present invention: 0.5 * Cu / S '10, a cooling rate below 300 ° C / min produces a temperature greater than Oj um Thick CuS precipitates. That is, when the cooling rate increases, several nuclei are generated, so the CuS precipitate changes fine. When the composition of Cii and S has a relationship: 0.5 * Cu / S > 10 Reheating 21 200533765 The number of coarse precipitates in an incompletely dissolved state increased during the treatment. Therefore, increasing the cooling rate will not cause an increase in the number of cores. Therefore, CuS Shen Dianwu will not change the details (Figure 3c '0.0039% 0.001% p; 0.0005% S; 0.03% A1; 0.0015% N; and 0.28% Cu). 5 Refer to Figures 3a to 3c, because increasing the cooling rate results in finer CuS Shen Dianwu's therefore does not need to provide the upper limit of the cooling rate. However, even when the cooling rate is 1,000 ° c / min or more, the CuS precipitate has not been further reduced in size, so the cooling rate is more preferably 300 ~ 1, 〇〇〇 its / min range. Figures 3a and 3b (0.0043% C; 0.01% p; 0055% S; 10 ％ 。3% of A1; 0.0024% of N; and 0.081% of Cu) individually show the case of 0.5 * Cu / S $ 3 and 0.5 * Cu / S > 3. As shown in the figure, it can be seen When the 0.5 * Cu / S value is 3 or less, a CuS precipitate having a size of 0 μm or less can be obtained more securely. In the case of MnCu sinking steel, the cooling rate is relatively slower. It is preferably 3015 ° C / min or more. Even when the composition of Mn, Cu, and S satisfies the relationship according to the present invention: 2S0.5 * (Mn + Cu) / S $ 20, which is less than 300. ° C / min cooling rate produces coarse precipitates with an average size greater than 0.2 um. That is, as the cooling rate increases, several nuclei are generated, so the precipitate changes finely. When the composition of Mn, Cu, and S has a relationship Formula: 0.5 * (Mn + Cu) / s > 20, 20 The coarse Shen Dianwu which is incompletely dissolved during the reheating treatment increases, so even if the cooling rate increases, the number of cores does not increase, so the precipitation is not Minor changes (Figure 4b, 0.0039% C; 0.4% Mn; 0.01% p; 0.01% S; 0.05% A1; 0.0016% N; and 0.15% Cu). Refer to Figures 4a and 4b Because increasing the cooling rate leads The result is a more subtle 22 200533765 Shen Dianwu '. Therefore, it is necessary to provide an upper limit of the cooling rate. However, even when the cooling rate is 1,000 ° c / min or more, the precipitate does not further reduce the size, so the cooling rate is more The best range is 300 ~ 1,000 ° C / min. [Winding conditions] 5 After the above-mentioned hot rolling, the winding treatment is preferably performed at a temperature of 700 ° C or less. When the coiling treatment is performed at a temperature higher than 700 ° C, the precipitate grows too coarse, and therefore, the baking hardenability of the steel is reduced. [Cooling conditions] The steel is cold rolled to a desired thickness, preferably a reduction rate of 50 to 90%. Because 10 is a reduction rate of less than 50%, a small amount of nuclei are generated during recrystallization annealing, and crystal grains are excessively generated during annealing. Therefore, the crystal grains are coarsened by annealing, resulting in reduced strength and formability. A cold reduction rate of more than 90% leads to the promoted formability, although excessive nucleus is generated, and therefore, crystal grains recrystallized by annealing become excessively fine, thereby reducing the ductility of the steel. 15 [Continuous annealing] Continuous annealing temperature plays an important role in determining the mechanical properties of the product. According to the present invention, 'continuous annealing is preferably performed at a temperature of 500 to 900 ° F. Continuous annealing at a temperature below 500 C produces crystalline particles resulting from excessively fine recrystallization, and therefore, desired ductility cannot be ensured. At temperatures greater than 90 ° (^^ 20 °, Binbin annealing produces coarse recrystallized crystalline particles, so the strength of the steel decreases. The maintenance time during continuous annealing is provided to complete the recrystallization of the steel. The recrystallization effect of steel is about 退 for more than one hour. The present invention will be described in detail with reference to the following examples. 23 200533765 In the following examples, cold-rolled steel sheets are based on ASTM standards (ASTM E-8). Standard) Mechanically processed into a standard sample, and its mechanical properties are measured. Mechanical properties are obtained by using a tensile strength tester (available from INSTRON, model 6025). In mechanical strength, after the sample receives 5 2% strain After 20 minutes of heat treatment at 120 ° C, the post-baking yield strength is measured. The plastic-anisotropy index (rm value) and in-plane anisotropy index (r value) are based on the following equations ⑴ and (2 ) Obtained: = (r0 + 2 r45 + r9〇) / 4 ---- (1) r = (r0-2 r45 + r9〇) / 2-(2) 10 At the same time, the average size of the precipitate The number and number are obtained after measuring the size and number of all Shen Dianwu existing in the matrix. Example ll] The MnS precipitated steel is to provide the MnS precipitated steel according to the present invention. After the steel plate shown in Table 1 is reheated at a temperature of 1,200 ° C, the steel plate is then fine-rolled to provide 15 liters. The hot-rolled steel sheet was cooled at a cooling rate of 200 ° C / min, and then wound at 650 C. Then, the hot-rolled steel sheet was cold-rolled at a reduction rate of 75%, and then the cold-rolled steel sheet was continuously annealed. The rolling system is performed at 9100c, which is higher than A1 · 3 transformation degree, and the continuous annealing is performed by heating the steel plate at a rate of 100c / s for 40 seconds to 750. (: and implemented. Exceptionally, for Table 8 shows 20 samples of 8 samples, which are reheated to 0,050 °. After finishing rolling, they are cooled at a cooling rate of 50 t / min, and then wound at 750 ° c. 24 200533765 Table 1

Sample No.-ΈΜΈΈ%) — C Μη Ρ S A1 N Mo Kl 0.003-0.005 0.05-0.2 0.015 0.005-0.03 0.01-0.1 0.004 0.01-0.2 10 A1 0.0035 0.1 0.01 0.009 0.04 0.0021-6.44 A2 0.0041 0.10 0.009 0.012 0.05 0.0030 -4.83 A3 0.0038 0.08 0.011 0.012 0.035 0.0023-3.87 A4 0.0044 0.1 0.01 0.006 0.02 0.0032-9.67 A5 0.0022 0.1 0.009 0.011 0.04 0.0038-5.27 A6 0.0039 0.43 > 0.01 0.008 0.05 0.0038-31.2 A7 0.0067 0.1 r〇.〇〇0.01 0.04 0.0028-5.8 A8 0.0024 0.4 0.07 0.01 0.04 0.0016 Ti 0.02 11.6 A9 0.0042 0.11 0.012 0.01 0.032 0.0018 0.02 6.38 A10 0.0038 0.1 0.01 0.008 0.035 0.0025 0.16 7.25 All 0.0045 0.08 0.011 0.011 0.04 0.0011 0.064 4.22 A12 0.0044 0.08 0.01 0.01 0.025 0.003 0.092 4.64 A13 0.0046 0.09 0.012 0.012 0.04 0.0015 0.27 4.35 Note: Rl = 0.58 * Mn / S Table 2 Sample No. Mechanically set AS (um) Note YS (Mpa) TS (MPa) El (%) r-value (rm) △ r-value (Δγ) PBYS (Mpa) DBTT (° C) A1 221 310 49 1.83 0.41 288 -70 0.13 IS A2 241 315 47 1.75 0.36 292 -70 0.14 IS A3 233 312 47 1.73 0.38 282 -70 0.12 IS A4 AC 245 328 45 1.69 0.31 301 .70 0.1 IS A5 A 209 Λ Λ 299 51 1.88 0.42 232 -70 0.11 cs Ao Λ 211 〇r 1 290 52 1.82 0.38 235 -70 0.59 cs A / Λ 0 25 1 329 42 ~ Τ3Γ ~ · 0.29 298 -70 0.12 cs Ao A 〇1 ο2 ^ 〇c 292 48 0.58 215.] 〇0.21 CVS Ay A 1 Λ 225 οηπ 3 12 Ο 1 Λ 49 Λ Ο " 0.35 273 -80 0.12 IS / \ 1 u Λ 1 1 ZZy 〇〇Γ j 1 υ 4δ 2.21 0.28 ~ TT〇-80 0.13 IS All Λ 1 O 235 318 ο 〇A 47 0.31 ~ 28l ~~ -80 0.11 IS A 1 ZA 1 ^ ZZ3ό 1 Ί ο 32U Ο Ο Ο 46 ^ Τΰ1 ~ 0.33 ~ 304 ~~ -80 0.1 IS A 1 j 151 328 46 ~ Γ73 ~ 0.35 ~ 305 ~~ 〇 \ J -80 0.12 cs Note: YS = Yield strength 'TS = Tensile strength, E1 = Yanyou i Bo · Hu M: Under as index, △ value: In-plane anisotropy rate, r-value. Plasticity-anisotropic inch, is = principal Invented steel, cdjm gas; #, AS = Shen Dianwu's average size ^,-Traditional steel as shown in Table 2, samples A1 ~ A4 have excellent yield strength extension 25 200533765 elongation 'and yield_ extension Sexual balance and hardenability. In addition, these samples have a high plastic anisotropy domain and a low in-plane anisotropy index, and therefore, provide excellent moldability. ^ Conversely, due to its low carbon content, sample A5 provides low back-bake yield strength. Due to its large size, the sample also has low post-bake yield strength. Due to its high carbon content, sample A7 # has a low elongation and plastic anisotropy index, thus providing a high possibility of cracking during the forming process. Due to its low post-baking yield strength and secondary operating embrittlement temperature, sample A8 (which is a traditional very low carbon nitrogen steel) offers 10 possibilities during impact. & Samples παA9 to A12 have excellent moldability and baking hardenability. In contrast, sample A13 had poor moldability due to the high addition amount of Mo. [实施 例 1-2] Steel with high strength MnS precipitation strengthened by solid solution is to provide steel with high strength MnS 15 precipitation with solid solution strength according to the present invention. After reheating at a temperature of 1,200 ° C and then finishing rolling the steel sheet to provide a hot-rolled steel sheet, the hot-rolled steel sheet was heated at 200 ° C. . It is cooled at a cooling rate per minute, and then it is wound at 65 (). Then, the hot-rolled steel sheet was cold-rolled at a reduced speed of 75%, and thereafter the cold-rolled steel sheet was continuously annealed. The finish rolling is performed at 910 C, which is higher than the Ar3 transition temperature, and the continuous annealing repair is performed by heating the steel plate at a rate of 10 C / sec for 20 seconds to 750 ° C. 26 200533765 Table 3

Sample No. Composition (wt%) C Μη Ρ Si Cr S A1 N Mo Rl 0.003- 0.005 0.05- 0.2 0.2 0.1-0.8 0.2-1.2 0.005 · 0.03 0.01-0.1 0.004 0.01- 0.2 10 B1 0.0035 0.08 0.052--0.006 0.04 0.0015-7.73 B2 0.0042 0.10 0.102--0.010 0.05 0.0026-5.8 B3 0.0039 0.08 0.151--0.012 0.035 0.0018-3.87 B4 0.0018 0.52 0.052--0.011 0.03 0.0039-29 B5 0.0058 0.44 0.11--0.011 0.05 0.0025-21.1 B6 0.0038 0.38 0.15--0.008 0.05 0.0028-31.2 B7 0.0039 0.09 0.009 0.24-0.006 0.05 0.0022-8.7 B8 0.0042 0.09 0.013 0.43-0.012 0.03 0.0026-4.35 B9 0.0035 0.1 0.011 0.62-0.009 0.035 0.0025-6.4 B10 0.0022 0.4 0.009 0.25-0.009 0.03 0.0042-25.8 B11 0.0077 0.42 0.01 0.44-0.011 0.04 0.0042-21.1 B12 0.0042 0.4 0.01 0.62-0.009 0.05 0.0039-25.8 B13 0.0044 0.1 0.01-0.35 0.007 0.04 0.0024-8.29 B14 0.0032 0.09 0.01-0.65 0.012 0.04 0.0032-4.35 B15 0.0038 0.11 0.012-0.82 0.017 0.05 0.0018-3.75 B16 0.0025 0.4 0.011-0.32 0.009 0.03 0.0017-25.8 B17 0.0059 0.43 0.01-0.62 0.012 0.05 0.0024-20.8 B18 0.0042 0.4 0.01-0.82 0.01 0.04 0.0019-31.2 B19 0.0044 0.1 0.05--0.008 0.034 0.0018 0.025 7.25 B20 0.0046 0.1 0.01 0.25-0.008 0.035 0.0032 0.028 7.25 B21 0.0034 0.11 0.011-0.33 0.009 0.034 0.0012 0.019 7.09 B22 0.0041 0.11 0.045 0.21 0.35 0.01 0.03 0.0022 0.08 6.38 B23 0.0038 0.1 0.048 0.18 0.35 0.012 0.042 0.0035 0.06 4.83 B24 0.0043 0.1 0.012 0.2 0.32 0.015 0.029 0.0018 0.04 3.87 Note: Rl = 0.58 * Mn / S 27 200533765 Table 4 Table 4

Sample No. Mechanical properties AS ㈣ Note YS (MPa) TS (MPa) El (%) r-value (rj Δτ-value (Δτ) PBYS (MPa) DBTT ro B1 252 362 43 1.65 0.25 304 • 70 0.13 IS B2 305 411 36 1.52 0.29 346 -50 0.12 IS B3 377 460 32 1.46 0.27 414 -40 0.09 IS B4 235 342 44 1.71 0.44 258 -60 0.59 cs B5 302 409 33 1.39 0.22 359 -60 0.73 cs B6 352 450 32 1.40 0.46 381 -40 0.59 cs B7 250 360 45 1.64 0.25 312 -80 0.09 IS B8 315 421 40 1.52 0.22 348 -60 0.11 IS B9 366 460 35 1.46 0.29 414 -50 0.11 IS B10 238 342 47 1.73 0.62 255 -70 0.52 cs B11 324 430 31 1.40 0.28 358 -60 0.45 cs B12 340 440 35 1.42 0.42 360 -40 0.62 cs B13 239 360 44 1.62 0.20 293 -80 0.09 IS B14 306 420 38 1.44 0.22 359 -60 0.10 IS B15 350 462 33 1.40 0.21 428 -50 0.09 IS B16 230 345 46 1.68 0.42 250 -70 0.42 cs B17 319 429 32 1.32 0.22 368 -60 0.35 cs B18 342 459 28 1.25 0.13 382 -40 0.42 cs B19 259 361 44 1.95 0.31 321 -80 0.12 IS B20 255 355 46 1.98 0.32 302 -80 0.1 IS B21 235 359 46 1.95 0.29 295 -80 0.09 IS B22 351 474 36 1.59 0.17 406 -60 0.1 IS B23 335 462 35 1.55 0.15 390 -60 0.11 IS B24 328 419 39 1.67 0.19 358 -70 0.09 IS Note · YS = yield strength, TS = tensile strength, El = elongation, r -Value: plasticity-anisotropy index, Δι · -value: in-plane anisotropy index, PBYS = post-baking yield strength, DBTT = 5 study the ductility of secondary operation embrittlement-transition temperature of embrittlement, AS = Average size of precipitates, IS = steel of the present invention, CS = steel for comparison, CVS = traditional steel [Examples 1-3] A1N precipitation strengthened MnS precipitated steel is provided to provide A1N according to the present invention. For precipitation-enhanced MnS-precipitated steel, the steel sheet shown in Table 5 is reheated to a temperature of 1,200 ° C and after 10, the steel sheet is finished rolled to provide the hot-rolled steel sheet, and the hot-rolled steel sheet is 200 ° C / min. Cool at a cooling rate and then wind at 650 ° C. Then, the hot-rolled steel sheet was cold-rolled at a reduction rate of 75% 28 200533765, and then the cold-rolled steel sheet was continuously annealed. Finish rolling is performed at 910 ° C, which is higher than the Ar3 transition temperature, and continuous annealing is performed by adding the steel sheet to a rate of 10 ° C / sec to 40 seconds to 750 ° C. Table 5 Sample No. Component (wt%) __ C Μη Ρ S Α1 Ν Mo Rl R-2 0.003- 0.005 0.05- 0.2 0.03- 0.06 0.005- 0.03 0.01- 0.1 0.005- 0.02 0.01- 0.2 10 1-5 C1 0.0045 0.1 0.035 0.01 0.04 0.0135-5.8 1.54 C2 0.0038 0.11 0.044 0.007 0.055 0.0079-9.11 3.63 C3 0.0042 0.08 0.053 0.009 0.055 0.0065-3.87 4.4 C4 0.0018 0.10 0.042 0.01 0.04 0.0014-5.8 14.9 C5 0.0075 0.09 0.04 0.011 0.008 0.0067-6.53 0.46 C6 0.0035 0.4 0.04 0.009 0.04 0.0083-25.8 2.51 C7 0.0047 0.11 0.044 0.009 0.044 0.011 0.03 7.09 2.08 C8 0.0037 0.1 0.042 0.01 0.05 0.012 0.064 5.8 2.17 C9 0.0044 0.09 0.04 0.01 0.042 0.01 0.15 5.22 1.05 C10 0.004 0.11 0.04 0.009 0.04 0.01 0.27 7.09 2.08

5 Note: Rl = 0.58 * Mn / S, R-2 = 0.52 * A1 / N Table 6 Sample mechanical strength AS Note, Thai number YS TS El r-value Ar-value PBYS DBTT (um) (MPa) (MPa) ) (%) (rm) (Δγ) (MPa) CC) Cl 242 358 44 1.71 0.31 283 -70 0.07 IS C2 224 355 43 1.75 0.38 280 -70 0.09 IS C3 239 360 40 1.68 0.29 302 -70 0.11 IS C4 210 330 46 1.78 0.32 269 -70 0.11 cs C5 228 352 37 1.52 0.25 295 -70 0.12 cs C6 228 360 40 1.65 0.54 280 -70 0.41 cs C7 246 362 45 2.09 0.34 298 -80 0.08 IS C8 220 350 46 2.18 0.42 287- 80 0.07 IS C9 230 357 44 2.00 0.32 276 -80 0.11 IS CIO 239 362 43 1.79 0.27 300 -80 0.1 cs 29 200533765 Anisotropy, E] = elongation, Γ-value: plasticity-anisotropy index △! * -Bo. Transformation ^ Plain embrittlement of the objects [Example 2-1] CuS-precipitated steel To provide the CuS-precipitated steel according to the present invention, the steel plate shown in Table 7 was reheated to 1,200 ° C After that, the steel sheet was finish-rolled to provide a hot-rolled steel sheet, the hot-rolled steel sheet was cooled at a cooling rate of 400 it / min, and then wound at 650 ° C. Then, the hot-rolled steel sheet was cold-rolled at a reduction rate of 75%, and thereafter the cold-rolled steel sheet was continuously annealed. Finish rolling is performed at 910 ° C, which is higher than the Ar3 10 transition temperature, and continuous annealing is performed by heating the steel at a rate of 10 ° C / sec for 40 seconds to 750 ° C. Exceptionally, for sample D7 in Table 7, after reheating to 1,050 ° C and subsequent finishing rolling, it was cooled at a cooling rate of 400 ° C / min and then wound at 650 ° C. For samples D8 to D11 in Table 7, after reheating to a temperature of 1,200 ° C and subsequent finishing rolling, it was cooled at a cooling rate of 450 ° C / min, and then wound at 650 ° C. 20 30 25 200533765 Table 7 sample compilation " 5 tiger. Composition (% by weight) CPS A1 N Cu Mo R-3 0.003-0.005 0.015 0.003-0.025 0.01-0.1 0.004 0.01-0.2 0.01-0.2 MO D1 0.0038 0.01 0.01 0.04 0.0025 0.035-1.75 D2 0.0045 0.009 0.008 0.04 0.0026 0.045-2.81 D3 0.0035 0.011 0.006 0.03 0.0012 0.06-5.0 D4 0.0042 0.009 0.005 0.04 0.0027 0.083-8.3 D5 0.0016 0.011 0.009 0.05 0.0038 0.05-2.78 D6 0.0037 0.00 0.008 0.04 0.0015 0.25-15.6 D7 0.0078 0.010 0.012 0.04 0.0024 0.064-2.67 D8 0.0035 0.011 0.009 0.024 0.0035 0.038 0.018 2.11 D9 0.0043 0.009 0.011 0.043 0.0026 0.04 0.083 1.82 D10 0.0039 0.01 0.01 0.038 0.0042 0.062 0.17 3.1 D11 0.004 0.012 0.011 0.028 0.0032 0.053 0.25 2.41

Note: R-3 = 0.5 * Cu / S

Table 8 Sample port, Green No. Mechanical strong Wan AS (um) Note YS (Mpa) TS (MPa) El (%) r-value (rj △ r-value (Δγ) PBYS (MPa) DBTT ro D1 219 310 49 1.88 0.41 265 -70 0.08 IS D2 224 325 47 1.83 0.36 275 -70 0.08 IS D3 225 330 45 1.79 0.38 289 -70 0.07 IS D4 240 335 45 1.75 0.30 311 -70 0.09 IS D5 205 290 50 1.88 0.46 235 -70 0.09 cs D6 216 299 49 1.80 0.38 240 -70 0.48 cs D7 256 339 40 1.53 0.29 320 -70 0.08 cs D8 214 310 48 2.10 2.9 260 -70 0.07 IS D9 228 320 47 2.01 3.1 271 -70 0.07 IS DIO 220 325 46 1.99 2.7 279 -70 0.08 IS Dll 219 319 48 1.71 2.6 285 -70 0.1 cs

5 Note: YS = yield strength, TS = tensile strength, Η = elongation, r-value: plasticity-anisotropy index, △! *-Value: in-plane anisotropy index, PBYS = post-baking yield strength DBTT = ductility used to study the embrittlement of the secondary operation-brittle transition temperature, AS = average size of precipitates, 1S = steel of the present invention, CS = steel for comparison [Example 2-2] with solid solution Solidified high strength CuS precipitated steel is to provide high strength C Vi S Shen 10 precipitated steel with solid solution strengthening according to the present invention. The steel plate shown in Table 9 is reheated to 1,200 ° C. After that, the steel sheet was finish-rolled to provide a hot-rolled steel sheet, the hot-rolled steel sheet was cooled at a cooling rate of 400 ° C / 31 200533765 minutes, and then wound at 650 ° C. Then, the hot-rolled steel sheet was cold-rolled at a reduction rate of 75%, and thereafter the cold-rolled steel sheet was continuously annealed. Finish rolling is performed at 910 ° C, which is higher than the Ar3 transition temperature, and continuous annealing is performed by heating the steel at a rate of 10 ° C / second for 40 seconds to 750 ° C. 5 Table 9 samples, No. ▲▲. Components (% by weight) CP Si Cr S A1 N Cu Mo R-3 0.003- 0.005 0.2 0.1-0.8 0.2-1.2 0.003- 0.025 0.01-0.1 0.004 0.01-0.2 0.01-0.2 MO E1 0.0038 0.050--0.006 0.04 0.0025 0.095-7.92 E2 0.0046 0.11--0.008 0.03 0.0026 0.06-3.75 E3 0.0033 0.148--0.01 0.04 0.0018 0.038-1.9 E4 0.0018 0.050--0.011 0.04 0.0024 0.054-2.45 E5 0.0065 0.115-- 0.009 0.03 0.0025 0.082-4.56 E6 0.0038 0.15--0.006 0.05 0.0028 0.25-20.8 E7 0.0039 0.01 0.25-0.006 0.04 0.0026 0.1-8.25 E8 0.0042 0.011 0.45-0.008 0.05 0.0016 0.086-5.35 E9 0.0035 0.015 0.65-0.012 0.05 0.0028 0.051-2.14 E10 0.0018 0.009 0.25-0.009 0.03 0.0042 0.077-4.28 E11 0.0077 0.011 0.42-0.011 0.04 0.0042 0.046-2.09 E12 0.0042 0.01 0.62-0.007 0.05 0.0039 0.252-18 E13 0.0035 0.009-0.34 0.005 0.05 0.0014 0.08-8.00 E14 0.0038 0.011-0.62 0.01 0.04 0.0022 0.09-4.5 E15 0.0045 0.01-0.83 0.018 0.04 0.0028 0.08-2.22 E16 0.0016 0.01-0.34 0.011 0.03 0.0017 0.0 8-3.64 E17 0.0072 0.009-0.59 0.008 0.04 0.0026 0.12-7.5 E18 0.0035 0.012-0.80 0.005 0.05 0.0013 0.26-26 E19 0.0045 0.054--0.008 0.024 0.0022 0.06 0.02 3.75 E20 0.0036 0.011 0.27-0.008 0.034 0.0028 0.06 0.018 3.75 E21 0.0032 0.01 -0.32 0.011 0.035 0.0025 0.054 0.022 1.23 32 200533765 Note: R-3 = 0.5 * Cu / S Table 10

Sample number Λ / C ^ ---------- «Π Mechanical properties AS (MPa) TS (MPa) El r-value (rm) △ r-value (Δγ) PBYS (MPa) DBTT ro ㈣ King 5 E1 248 360 43 1.70 0.28 310 -70 0.09 IS E2 308 405 ~ τΓ 1.58 0.28 340 -50 0.08 IS E3 367 465 33 1.46 0.26 410 -40 0.07 IS E4 230 340 45 1.70 0.44 262 -60 0.49 cs E5 322 415 30 1.35 0.20 365 -60 0.73 cs E6 345 445 32 1.40 0.46 380 -40 0.59 cs E7 250 350 47 1.69 0.23 318 -80 0.09 IS E8 325 415 42 1.55 0.22 368 -60 0.08 IS E9 356 465 35 1.44 0.21 424 -50 0.08 IS E10 238 352 47 1.69 0.58 250 -70 0.45 cs E11 325 425 32 1.40 0.28 358 -60 0.45 cs E12 345 445 32 1.42 0.42 370 -40 0.62 cs E13 242 365 43 1.69 0.21 302 -80 0.09 IS E14 310 425 ^ 38 1.46 0.23 365 -60 0.08 IS E15 352 454, 36 1.45 0.21 408 -70 0.07 IS E16 " T '1 〇230 345 46 1.68 0.32 265 -70 0.07 cs Ε17 315 413 28 1.32 0.22 365 -60 0.09 cs Ε18 348 461 27 1.24 0.13 372 -60 0.42 cs Ε19 ΙΓΟ A 254 365 43 2.08 2.8 322 -70 0.09 IS bzU mi 247 348 48 1.95 0.28 295 -80 0.09 IS t21 240 35 Factory 45 1.93 0.27 298 -80 0.07 IS Note: YS = Yield of Strong Tang 5 Anisotropy index strength, E1 = elongation, r-value: plasticity-anisotropy index, Ar-value: in-plane transition temperature, AS evening f / f yield strength, DBTT = ductility used to study the embrittlement of the secondary operation-brittleness-, the size of the nine thousand materials, IS = the steel of the present invention, CS = the steel used for comparison [贯 施Example 2-3] A1N precipitation strengthened CuS precipitated steel is provided to provide the A1N precipitation strengthened cus precipitated steel according to the present invention. 'The steel plate shown in Table 11 is reheated to a temperature of UOO t and the temperature of After finishing rolling the steel sheet to provide a hot-rolled steel sheet, the hot-rolled steel sheet is cooled at a cooling rate of 400 it / min, and then wound at 650 t. Then, the hot-rolled steel sheet was cold-rolled at a reduction rate of 75%, and thereafter the cold-rolled steel sheet was continuously annealed. Finish rolling is performed at 910 33 200533765 ° C, which is higher than the Ar3 transition temperature, and continuous annealing is performed by heating the steel at a rate of 10 ° C / sec for 40 seconds to 750 ° C. Exceptionally, for samples F8 to F10 in Table 11, after reheating to 1,200 ° C and subsequent finishing rolling, these samples were cooled at a cooling rate of 550 ° C / min and then at 5 650 ° C Coiled. Table 11 Sample No. Component (wt%) CPS A1 N Cu Mo R-3 R-2 0.003- 0.005 0.03- 0.06 0.003- 0.025 0.01- 0.1 0.005- 0.02 0.01- 0.2 0.01- 0.2 MO 1-5 F1 0.0042 0.041 0.005 '' 0.045 0.0125 0.09-9 1.87 F2 0.0035 0.042 0.008 0.05 0.0072 0.052-3.25 3.61 F3 0.0045 0.043 0.014 0.04 0.0052 0.07-2.5 4 F4 0.0015 0.04 0.01 0.05 0.0014 0.08-4 18.6 F5 0.0073 0.037 0.008 0.01 0.0077 0.1-6.25 0.68 F6 0.0036 0.042 0.006 0.04 0.0083 0.155-12.9 2.51 F7 0.0037 0.044 0.011 0.055 0.012 0.09 0.018 4.09 2.38 F8 0.0043 0.04 0.009 0.045 0.0092 0.088 0.078 4.89 2.54 F9 0.0035 0.044 0.012 0.054 0.011 0.097 0.16 4.04 2.55 F10 0.0045 0.042 0.008 0.053 0.0084 0.082 0.25 5.13 3.28

Note: R-2 = 0.52 * Α1 / Ν, R-3 = 0.5 * Cu / S 10 34 200533765 Table 12

Sample number Mechanical properties AS (um) Note YS (MPa) TS (MPa) El (%) r-value (rm) △ r-value (△ r) PBYS (MPa) DBTT ro F1 240 353 45 1.70 0.32 296 -70 0.06 IS F2 232 350 44 1.72 0.28 291 -70 0.07 IS F3 245 362 46 1.80 0.27 323 -70 0.05 CS F4 216 340 46 1.78 0.35 260 -70 0.08 CS F5 243 360 35 1.49 0.25 308 -70 0.07 CS F6 238 355 43 1.69 0.44 253 -70 0.41 CS F7 235 348 46 1.94 0.24 296 -70 0.06 IS F8 237 355 44 1.93 0.22 302 -70 0.08 IS F9 237 360 46 1.97 0.26 312 -70 0.06 IS F10 231 346 46 1.70 0.27 300 -70 0.07 CS Note: YS = yield strength, TS = tensile strength, El = elongation, r-value ·· plasticity-anisotropy index, Δτ * -value ·· in-plane anisotropy index, PBYS = post-bake yield Strength, DBTT = ductility used to study embrittlement in the secondary operation-brittle 5 transition temperature, AS = average size of precipitates, IS = steel of the invention, CS = steel for comparison [Example 3-1] MnCu The precipitated steel is to provide the MnCu precipitated steel according to the present invention. The steel plate shown in Table 13 is reheated to a temperature of 1,200 ° C and thereafter the steel plate is finish-rolled to improve the temperature. After the hot rolled steel sheet, hot rolled steel sheet to 600 ° C / per cooling rate, then after 10 wound 650 ° C. Then, the hot-rolled steel sheet was cold-rolled at a reduction rate of 75%, and thereafter the cold-rolled steel sheet was continuously annealed. Finish rolling is performed at 910 ° C, which is higher than the Ar3 transition temperature, and continuous annealing is performed by heating the steel at a rate of 10 ° C / second for 40 seconds to 750 ° C. 15 35 200533765 Table 13 Sample number component (weight 1 y%) C Μη Ρ S Α1 N Cu Mo R-4 R-5 0.003- 0.005 0.03-0.2 0.015 0.003- 0.025 0.01-0.1 0.004 0.01-0.2 0.01-0.2 0.3 2-20 G1 0.0041 0.08 0.012 0.02 0.05 0.0013 0.03-0.11 2.75 G2 0.0038 0.1 0.009 0.012 0.04 0.0021 0.04-0.14 5.83 G3 0.0044 0.15 0.01 0.015 0.04 0.0024 0.05-0.2 6.67 G4 0.0042 0.17 0.008 0.009 0.04 0.0012 0.12-0.29 16.1 G5 0.0012 0.12 0.01 0.012 0.05 0.0014 0.05-0.17 7.08 G6 0.0064 0.15 0.009 0.01 0.04 0.0023 0.03-0.18 9.0 G7 0.0042 0.45 0.01 0.011 0.05 0.0013 0.18-0.63 28.6 G8 0.0035 0.11 0.011 0.02 0.045 0.0032 0.03 0.019 0.14 3.5 G9 0.0033 0.12 0.01 0.014 0.034 0.0019 0.046 0.082 0.17 5.93 G10 0.0043 0.12 0.014 0.009 0.027 0.0034 0.062 0.16 0.18 10.1 G11 0.0045 0.15 0.008 0.014 0.033 0.0032 0.085 0.25 0.24 8.39

Note: R-4 = Mn + Cu, R-5 = 05 * (Mn + Cu) / S Table 14

[Example 3 · 2] The steel with solid solution strengthening and high strength MnCu precipitation is a steel provided with Mn Cu precipitation with solid solution strengthening and high strength according to the present invention. The steel plate shown in Table 15 After reheating to a temperature of 1,200 ° C 36 10 200533765 degrees and thereafter finishing the steel sheet to provide a hot-rolled steel sheet, the hot-rolled steel sheet was cooled at a cooling rate of 600 ° C / min, and then wound at 650 ° C. Then, the hot-rolled steel sheet was cold-rolled at a reduction rate of 75%, and thereafter the cold-rolled steel sheet was continuously annealed. The finish rolling is performed at 910 ° C, which is higher than the Ar3 transition temperature, and the continuous annealing system 5 is performed by heating the steel at a rate of 10 ° C / second for 40 seconds to 750 ° C. 10 15 20 37 200533765 Table 15 Sample composition (% by weight) Product C Μη Ρ Si Cr SA] N Cu Mo R-4 R-5 Edit 0.003- 0.03- 0.2 0.1- 0.2- 0.003- 0.0 Ι 0.005- 0.01- 0.3 2-No. 0.005 0.2 0.8 1.2 0.025 〇. 1 0.004 0.2 0.2 20 H1 0.0042 0.06 0.039--0.015 0.05 0.0025 0.02 0.08 2.67 H2 0.0045 0.1 0.041--0.018 0.04 0.0023 0.03-0.13 3.61 H3 0.0037 0.12 0.09--0.016 0.05 0.0032 0.04 0.16 5 H4 0.0045 0.18 0.14--0.011 0.04 0.0028 0.1-0.28 12.7 H5 0.0018 0.1 0.04--0.012 0.05 0.0024 0.1-0.2 8.33 H6 0.0075 0.15 0.1--0.012 0.03 0.0022 0.06-0.21 8.75 H7 0.0043 0.3 0.14--0.008 0.04 0.0015 0.15 0.45 28.1 H8 0.004 0.09 0.04--0.013 0.035 0.0029 0.028 0.017 0.12 4.54 H9 0.0044 0.11 0.094--0.012 0.026 0.0035 0.047 0.072 0.16 6.54 H10 0.0037 0.12 0.145--0.01 0.042 0.0018 0.088 0.16 0.21 10.4 H11 0.0045 0.08 0.043--0.009 0.037 0.0032 0.035 0.25 0.16 6.39 H12 0.0041 0.06 0.01 0.18-0.018 0.04 0.0019 0.04-0.1 5 H13 0.0036 0.1 0.009 0.17-0.015 0.05 0.0026 0.0 3-0.13 7.22 H14 0.0038 0.13 0.012 0.35-0.015 0.04 0.0032 0.03-0.16 6.67 H15 0.0045 0.22 0.012 0.55-0.01 0.04 0.0032 0.05-0.27 13.5 H16 0.0021 0.12 0.009 0.2-0.011 0.05 0.0024 0.12-0.24 10.9 H17 0.0064 0.12 0.01 0.34-0.012 0.04 0.0028 0.07-0.19 7.9 H18 0.0044 0.25 0.012 0.53-0.009 0.05 0.0022 0.18-0.43 23.9 H19 0.0039 0.11 0.012 0.21-0.014 0.034 0.0029 0.044 0.017 0.15 5.5 H20 0.0045 0.12 0.009 0.32-0.011 0.042 0.0042 0.038 0.075 0.16 7.18 H21 0.0036 0.14 0.012 0.62 0.62 -0.009 0.033 0.0022 0.063 0.16 0.20 11.3 H22 0.0042 0.09 0.013 0.2-0.01 0.038 0.0033 0.053 0.25 0.14 7.15 H23 0.0044 0.07 0.009-0.25 0.017 0.04 0.0018 0.03-0.1 2.94 H24 0.0039 0.Π 0.01-0.24 0.015 0.03 0.0022 0.03-0.14 4.67 H25 0.0042 0.15 0.011-0.55 0.015 0.04 0.0023 0.05-0.2 6.67 H26 0.0046 0.18 0.012-0.86 0.01 0.04 0.0016 0.04-0.22 11 38 200533765 H27 0.0022 0.15 0.01-0.24 0.015 0.04 0.0026 0.1-0.25 8.33 H28 0.0067 0.15 0.012-0.52 0.011 0.05 0.0025 0.11 -0. 26 11.8 H29 0.0043 0.2 0.009-0.88 0.008 0.03 0.0013 0.15-0.35 21.9 H30 0.0039 0.09 0.012-0.23 0.012 0.034 0.0028 0.043 0.019 0.13 5.54 H31 0.0045 0.12 0.01-0.58 0.013 0.042 0.0033 0.056 0.079 0.18 6.77 H32 0.0037 0.15 0.009-0.83 0.011 0.023 0.0021 0.0021 0.063 0.17 0.21 9.68 H33 0.0042 0.1 0.011-0.22 0.011 0.035 0.0031 0.073 0.27 0.17 7.86

Note: R-4 = Mn + Cu, R-5 = 05 * (Mn + Cu) / S Table 16 Sample No. Mechanical properties AS PN (number / mm 2) Note YS (Mpa) TS (MPa) El (%) r-value (rm) △ r-value (△ r) PBYS (MPa) DBTT (° C) H1 265 360 49 1.98 0.25 346 -70 0.05 5.5X10S " IS H2 258 358 50 1.92 0.28 345 -70 0.05 4.0X10s IS H3 308 410 43 1.71 0.21 394 -60 0.06 2.2X10C IS H4 335 442 37 1.60 0.19 428 -50 0.11 9.5X1 ϋΰ IS H5 255 350 49 1.92 0.31 295 -70 0.06 4.3Xl (f — cs H6 304 400 35 1.45 0.25 382 -60 0.06 3.5X10S cs H7 351 454 32 1.38 0.22 395 -40 0.61 2.3X104 cs H8 258 360 49 2.35 0.28 345 -70 0.06 4.6X10s IS H9 311 408 44 1.98 0.21 389 -60 0.05 3.3Xl〇s IS H10 330 445 38 1.82 0.2 422 -50 0.09 9.5X107 IS H11 264 364 47 1.91 0.22 350 -70 0.06 4.7X10C cs H12 245 350 50 1.85 0.28 338 -80 0.06 4.5X10s IS H13 253 355 49 1.83 0.29 342 -80 0.07 2.5X103 IS H14 293 405 45 1.65 0.21 390 -60 0.06 4.0X103 IS H15 355 453 38 1.51 0.22 435 -60 0.09 9.1X10 ° IS H16 234 342 52 1.85 0.33 275 -80 0.09 4.2X106 cs H17 308 412 36 1.48 0.21 398 -70 0.09 3.2X10C cs H18 335 448 34 1.38 0.57 380 -60 0.51 9.3X104 cs H19 240 352 50 2.28 2.9 335 -80 0.05 8.2X10g IS H20 303 410 44 1.88 2.1 387 -60 0.06 4.5X10G IS H21 359 460 37 1.7 2.0 437 -60 0.08 4.1X10 ° IS H22 252 359 50 1.86 2.2 339 -80 0.07 4.5X10G cs H23 250 355 48 1.89 0.28 335 -80 0.06 9.5Xl (f IS H24 245 355 47 1.85 0.27 348 -80 0.06 6.5X10s IS H25 288 395 46 1.69 0.25 375 -60 0.07 2.1Xl (f IS H26 348 443 37 1.54 0.21 420 -60 0.09 7.5X106 IS H27 244 345 46 1.88 0.36 283 -80 0.09 5.2X10g cs H28 297 402 33 1.45 0.21 365-70 0.09 3.2X103 cs H29 345 454 33 1.36 0.47 385 -60 0.51 9.3X104 cs H30 252 358 48 2.15 0.24 330 -80 0.07 8.3X102 IS H31 292 390 43 1.92 0.2 372 -60 0.09 3.2 × 1ϋβ 'IS H32 343 448 38 1.72 0.18 421 -60 0.07 7.5X10 ° IS H33 251 357 47 1.79 0.2 341 -80 0.06 6.5X10 ° cs

Note: YS = yield strength, TS = tensile strength, Η = elongation, r-value: plastic-anisotropic index, Ar-value: in-plane 5 anisotropy index, PBYS = post-bake yield strength, DBTT = Ductility used to study embrittlement in the secondary operation-brittle transition temperature, AS = average size of Shen Dianwu, PN = number of Shen Dianwu, IS = steel of the present invention, CS = steel for comparison [Example 3- 3] A1N precipitation strengthened MnCu precipitated steel 39 200533765 In order to provide the A1N precipitation strengthened MnCu precipitated steel according to the present invention, the steel plate shown in Table 17 is reheated to a temperature of 1,200 ° C and thereafter After finishing rolling the steel sheet to provide a hot-rolled steel sheet, the hot-rolled steel sheet is cooled at a cooling rate of 400 t / min, and then wound at 650 ° C. Then, the hot-rolled steel sheet was cold-rolled at a reduction rate of 75% 5, and thereafter the cold-rolled steel sheet was continuously annealed. Finish rolling is performed at 910 ° C, which is higher than the Ar3 transition temperature, and continuous annealing is performed by heating the steel at a rate of 10 ° C / second for 40 seconds to 750 ° C. Sample No. ▲ in Table 17 (% by weight) C Mn PS A1 N Cu Mo R-4 R-5 R-2 0.003- 0.005 0.03- 0.2 0.03- 0.06 0.003- 0.025 0.01- 0.1 0.005- 0.02 0.01- 0.2 0.01 -0.2 0.3 2-20 1-5 11 0.0042 0.07 0.038 0.02 0.032 0.0085 0.03-0.1 2.5 1.96 12 0.0038 0.1 0.042 0.015 0.042 0.0072 0.03-0.13 4.33 3.03 13 0.0045 0.14 0.037 0.015 0.055 0.0092 0.05-0.19 6.33 3.11 14 0.0045 0.2 0.05 0.009 0.07 0.008 0.05-0.25 13.9 4.55 15 0.0015 0.17 0.04 0.012 0.042 0.0072 0.05-0.22 9.17 3.03 16 0.0062 0.15 0.038 0.015 0.038 0.0014 0.12-0.27 9 14.1 17 0.0036 0.25 0.042 0.009 0.04 0.0083 0.2-0.45 25 2.51 18 0.0035 0.09 0.04 0.012 0.052 0.0093 0.043 0.019 0.13 5.54 2.91 19 0.0046 0.11 0.039 0.011 0.053 0.011 0.053 0.082 0.16 7.41 2.51 110 0.0038 0.12 0.042 0.012 0.061 0.012 0.085 0.16 0.21 8.54 2.64 111 0.004 0.12 0.045 0.01 0.059 0.0095 0.065 0.26 0.19 9.25 3.23

Note: R-2 = 0.52 * A1 / N, R-4 = Mn + Cu, R-5 = 05 * (Mn + Cu) / S 40 10 200533765 Table 18 Sample Margin ΤΓ ΊΤ ΊΤ ir 15 " 16 ~

ΊΤ IT 19 ~ Ho · nr YS (Mpa) ~ 250 " 145 " 248 " ~ 254 "

~ 2W " 25Γ

~ WT ~ 251 ~ 2A5 " 250 ~ TS (MPa) " 355 "

355 " ~ 35T " 348 " " 342 "

~ 36T ^ 352 " 350 "

" 359 " ~ 3W

15T (%) ~ 48 ~ irf ^ 47 ~ 45 ~ ~ 46 ~

40 ^ 4T

49 ~ 4T r-value (rm) 1.85 1.89 1.84 1.88 1.55 1.66 " 2ΤΓ 2.13 2.15 1.80 Δγ-value (Ar) 0.28 WT W3

OJT ~ 03S ΈΤΓ ^ 025 ~ 024 " 03Σ ΌΓ PBYS (MPa)

" 34Γ 14F Ί30 " " 280 " " 33Γ ~ 29T " 339 "

~ 340 ~ 33T " 33Γ DBTT (° C) • 80 10 ~ ^ 60 ~ ^ 80- -70 • 80 ^ 60 AS (um) ~ 〇M Έ06 ΟΌΤ

0 ^ 9 " 'OW 0Ό9

03T 0Ό6 0O6 ~ ~ 〇M 0Ό9 Note

" 93XIF 163X10 ^ TTXTO8 T5X! 〇 ^ " 12X10 ^ " T2χτσ IgjXTa 8MT〇 ^ TSXTO ^ uxio ^ Τ5ΧΓ06

IS

IS

IS

IS cs cs cs

IS

IS

IS Although the preferred embodiment of the present invention has been disclosed for illustrative purposes: But those skilled in the art will understand various modifications, additions and substitutions that do not depart from the scope of the present invention disclosed in the scope of the attached patent application And the mental system can be dagger 0010 [Schematic description] Figures la to lc are diagrams showing the relationship between the solid solution carbon content in the crystalline particles and the size of the precipitates, where the figure la shows the MnS precipitation Fig. 1b shows the situation of CuS precipitated steel, and Fig. 1c shows the situation of MnCu sinking steel; 15 2 & and 213 are diagrams showing the relationship between the size of MnS precipitates and the cooling rate Figure 2a shows the case of 0.58 * Mn / S < 10, and Figure 2b shows the case of 0.58 * Mn / S >10; Figures 3a to 3c show CuS precipitate size and cooling rate A graphical representation of the relationship between them, where Figure 3a shows the case of 0.5 * Cu / s = 2.56, Figure 2b shows the case of 0.5 * Cu / S = 8.1, and Figure 3c shows 0.5 * Cu / S = 28; 41 200533765 Figures 4a and 4b show the size and coldness of MnS, CuS and (Mn, Cu) S precipitates. It illustrates the relationship between the rate, wherein the first 4a FIG display 2 $ 0.5 * (Mn + Cu) / S $ case 20 of, and on Figure 4b show 0.5 * (Mn + Cu) / S > 20 cases of. 5 [Description of main component symbols] (none)

42

Claims (1)

200533765 10. Scope of patent application: 1. A baking-hardenable cold-rolled steel sheet with excellent formation, including: 0.003 to 0.005% C; 0.003 to 0.03% S; 0.01 to 〇_1% A1; 0.02 % Or less of N; 0.2% or less of P; 0.03 to 0.2% of Mη and 5 0.005 to 0.2% of Cu; and the balance of Fe and other inevitable impurities, which Based on weight, when the steel plate contains one of Mn and Cu, the composition of Mn, Cu, and S satisfies the relationship: 0.58 * Mn / SS 10 and 1 ^ 0.5 * Cu / SSl0, and when the steel plate contains For both Mη and Cu, the composition of Mu, Cu, and S satisfies the relationship: Mn + Cu S 0.3 and 2 $ 10 0.5 * (Mn + Cu) / s $ 20, and among them, MnS, CuS, and (Mn, Cu) S Shen Dianwu has an average size of 0.2um or less. 2, A kind of cold rolled steel sheet with excellent impurities for baking hardening, including: 0.003 ~ 0.005% C; 〇〇〇〇5 〇〇〇3% & 〇〇1 ~ 〇 ″% A1; 0.02 % Or less of n; 0.2% or less of p; 005 ~ 02%; and 15 Fe and other unavoidable impurities f, which are based on weight%, wherein, Mn and The composition of S satisfies the relationship: 〇58 * Mn / sg 10, which is based on the weight, and wherein the precipitate of MnS has an average size of 0um or less. 3. The steel sheet according to item 2 of the scope of patent application, wherein the steel sheet contains 0.015% or less of P. 20 4_ The steel sheet as claimed in the May 2 patent scope, wherein the steel sheet contains 0.004% or less of N. 5. The steel sheet according to item 2 of the scope of patent application, wherein the steel plate contains P03 ~ 0.2% of P 0. The steel sheet according to item 2 of the scope of patent application, wherein the steel plate further includes 43 200533765 0.1 to 0. At least one of 8% Si and 0.2 to 2% Cr. 7. The steel sheet according to item 2 of the patent application scope, wherein the steel sheet includes 0 005 to 0.02% N and 0.03 to 0.06% ρ. 8. The steel sheet according to item 7 of the scope of the patent application, wherein the composition of Ai and ν satisfies a 5 foot relation ... 1 ^ 0 · 52 * A1 / ΚΓ: ^ 5. 9. The steel sheet according to any one of the items 2 to 8 of the scope of application for a patent, wherein the steel sheet further contains 0.01% to 0.2%] \ 40. 10 · —Bake-hardenable cold-rolled steel sheet with excellent formability, including: 0.003 to 0.005% C; 〇 · 〇〇3 to 0.025% of S; 0.01 to 0.08% of 10Al; 0 · 02 % Or less of N; 0.2% or less of P; 0.01 ~ 0.2% of Cu; and the balance of Fe and other unavoidable impurities, which are based on weight%, where the composition of 'Cu and S meets Relation formula: bo.vcu / suo, which is by weight 'and wherein the CuS precipitate has an average size of 0.1 um or less. 11. The steel sheet according to item 10 of the patent application scope, wherein the steel sheet contains 0,015% or less of P. 12. The steel sheet as claimed in claim 10, wherein the steel sheet contains 0.004% or less of N. 13. The steel plate as claimed in claim 10, wherein the composition of Cii and S satisfies the relationship: 1 $ 0.5 * Cu / S £ 3. 20 14 · The steel sheet according to item 10 of the scope of patent application, wherein the steel plate contains 0.03 ~ 0.2% of P ○ 15. The steel sheet according to item 10 of the scope of patent application, wherein the steel plate includes 0.1 At least one of 0.8% Si and 0.2 to L2% & 16. The steel sheet according to item 10 of the patent application scope, wherein the steel sheet contains 0.005 44 200533765 to 0.02% N, and 0.03 to 0.06% P. 17. The steel sheet according to item 16 of the scope of patent application, wherein the composition of A1 and N satisfies the relationship: 1 $ 0.52 * A1 / N ^ 5. 18. The steel sheet according to any one of claims 10 to π, wherein the 5 steel sheet further contains 0.01 to 0.2% Mo. 19. A bake-hardenable cold-rolled steel sheet having excellent formability, comprising: 0.003 to 0.005% C; 0.003 to 0.025% S; 0.01 to 0.08% A1; 0.02% or less N 〇 · 2% or less of P; 〇 · 〇3〜0 · 2% <Mn; 0.005 ~ 0.2% of Cu; and the balance of Fe and unavoidable impurities, which are based on 10% by weight, Among them, the composition of Mn, Cu, and S satisfies the relationship: Mn + CuSO.3 and 2 $ 0.5 * (Mn + Cu) / S $ 20, which are based on weight, and among them, MnS, CuS, and (Mn, Cu) The precipitate of S has an average size of 0.2 um or less. 20. The steel sheet according to item 19 of the scope of patent application, wherein the steel sheet contains 0.015% 15% or less of P. 21. The steel sheet as claimed in claim 19, wherein the steel sheet contains 0.004% or less of N. 22. For the steel sheet of the scope of application for item 19, wherein the number of the deposits is 2xl06 or more per unit area (mm2). 20 23. The steel sheet according to item 19 of the scope of patent application, wherein the composition of Mn, Cu, and S satisfies the relationship: 2 £ 0.5 * (Mn + Cu) / SS7. 24. For the steel plate in the scope of application for item 23, the number of the Shen Dianwu objects is 2 × 10 or more per unit area (mm2). 25. The steel sheet according to item 19 of the scope of patent application, wherein the steel plate contains 0.03 to 45 200533765 0.2% P 〇26. The steel sheet according to item 19 of the scope of patent application, wherein the steel plate further comprises 0.1 to 0.8 ° /. At least one of Si and 0.2 to 1.2% of Cr. 27. The steel plate according to item 19 of the scope of patent application, wherein the steel plate contains 0.005 5 to 0.02% of N and 0.03 to 0-6% of P. 28. The steel sheet as claimed in item 27 of the patent application, wherein the composition of A1 and N satisfies the relational formula: 1S0.52 * A1 / N $ 5. 29. The steel sheet according to any one of claims 19 to 28, wherein the steel sheet further contains 0.01 to 0.2% of Mo. 10 30 · —A method for manufacturing a bake-hardenable cold-rolled steel sheet with excellent formability, including the step of: after the steel sheet is reheated to a temperature of 1,100 ° C or more, with a transition temperature of Α * 3 Finishing rolling or more is performed by hot-rolling a steel sheet to provide a hot-rolled steel sheet, the steel sheet comprising: 0.003 to 0.005% C; 0.005 to 0.03% S, 0.01 to 0.005% A1 ; 〇2% or less of N; 0.2% or less of ρ; 15 0.05 ~ 2 · 2% 2Mη; and the balance of Fe and other inevitable impurities, which are based on weight%, Among them, the composition of Mn & S satisfies the relationship: 〇_58 * Mn / S $ 10, which is based on weight; it is 200. (] / Min or more to cool the steel sheet; coil the cooled steel sheet at a temperature of 700 ° C or less; cold-roll the steel sheet; and continuously anneal the cold-rolled steel sheet. 20 31 The method according to claim 30, wherein the steel sheet contains 0.015% or less of P. 32. The method according to claim 30, wherein the steel sheet contains 0.004% or more Less N. 33. The method of item 30 in the scope of patent application, wherein the steel sheet contains 0.03 ~ 46 200533765 0.2% P. 34. The method of item 30 in the scope of patent application, of which The steel sheet further comprises 0.1 to 0.8% of Si and 0.2 to 1.2%. At least one of 1 *. 35. The method according to item 30 of the scope of patent application, wherein the steel sheet contains 0.005 5 to 〇.〇 2% of N and 0.03 to 0.06% of P. 36. The method according to item 30 of the scope of patent application, wherein the composition of A and N satisfies the relationship: 1 $ 0.52 * A1 / NS5. 37. Such as The method according to any one of claims 30 to 36, wherein the steel sheet further comprises Mo in the range of 0.01 to 0.2 ° / 0. 10 38. Seed system Method for baking-hardenable cold-rolled steel sheet with excellent formability, comprising the steps of: after reheating the steel sheet to a temperature of 1,100 ° c or more, and finishing rolling the steel sheet at an Ar3 transition temperature or more Hot-rolled to provide a hot-rolled steel sheet, the steel sheet includes: 0.003 to 0.005% C; 0.003 to 0.025% S; 0.01 to 0.08% A1; 0.02% or less N; 0.2% or more Less than 15 Ρ; 〇.〇1 ~ 0.2% of Cu; and the balance of Fe and other unavoidable impurities, which are based on weight%, wherein the composition of Cu and S satisfies the relationship: 1 ^ 0.5 * Cu / S $ 10, by weight; cooling the steel sheet at a rate of 300 ° C / min or more; winding the cooled steel sheet at a temperature of 700 ° C or less; cold rolling the steel sheet; and The cold-rolled steel sheet is continuously annealed. 20 39. The method according to item 38 of the patent application, wherein the steel sheet contains 0.015% or less of P. 40. The method according to item 38 of the patent application, wherein the steel sheet Contains 0.004% or less of N. 41. The method of claim 38, wherein the composition of Cu and S is 47 200533765. Relation formula: $ 0.5 * Cu / SS3. 42. The method according to item 38 of the patent application, wherein the steel sheet contains 0.03 ~ 0.2% of P 〇 43. The method according to item 38 of the patent application, where The steel sheet further includes 5 ° ~~ ° 8 ° /. At least one of Si and 0.2 to 1.2% of Cr. 44. The method according to item 38 of the patent application scope, wherein the steel sheet contains 0.05 to 0.02% of N and 0.03 to 0.06 〇 / 〇 p. 45. The method of claim 38, wherein the composition of A1 & N satisfies the relationship: 1 $ 0.52 * A1 / N; ^ 5. 10 46. The method according to any one of claims 38 to 45, wherein the steel sheet further contains 0.01 to 0.2% Mo. 47. A method of manufacturing a bake-hardenable cold-rolled steel sheet with excellent formability, comprising the step of: when the steel sheet is reheated to a temperature of 1,100 or more, when the transition temperature is Ar3 or more The finishing rolling makes the steel sheet hot-rolled to provide a hot 15-rolled steel sheet. The steel sheet includes: The steel sheet includes: 0.003 to 0.005% of C; 0.003 to 0.025% of S; 0.01 to 0.08%. A1; 0.02 ° / 〇 or less N; 0.2% or less P; 0.03 to 0.2% Mn; 0.005 to 0.2% Cu; and the balance of Fe and other inevitable Impurities, which are based on weight%, wherein the composition of Mn, Cu, and S satisfies the relationship: Mn + Ci ^ 0.3 and 2O2s0.5 * (Mn + CuW2O, which is based on weight; Cool the steel plate at a rate of 300 ° C / min or more; wind the cooled steel plate at 700. (: or less; cold-roll the steel plate; and continuously anneal the cold-rolled steel plate. 48 · For example, the method of claim 47, wherein the steel sheet contains 0.015% or less of P. 48 200533765 49. The method of claim 47, wherein the steel sheet contains 0.004% or less of N. 50. The method according to item 47 of the patent application, wherein the number of deposits is 2 × 10 or more per unit area (mm2). 5 51. The method according to item 47 of the patent application, wherein the Mn, The composition of Cu and S satisfies the relational formula: 2 $ 0.5 * (Mn + Cu) / S ^ 7. 52. For the method of claim 51 in the scope of patent application, wherein the number of precipitates is per unit area (mm2) is 2xl08 or more. 53. The method according to item 47 of the patent application, wherein the steel plate contains 0.03 ~ 10 0.2% P. 54. The method according to item 47 of the patent application, wherein the steel plate It further comprises at least one of 0.1 to 0.8% of Si and 0.2 to 1.2% of Cr. 55. The method according to item 47 of the patent application scope, wherein the steel sheet contains 0.005 to 0.02% of N and 0.03 to 0.06% of P 15 56. The method of claim 55 in the scope of patent application, wherein the composition of A1 and N satisfies the relational formula: 1S0.52 * A1 / N $ 5. 57. As in any of the scope of claims 47 to 56 of the scope of patent application The method according to item 5, wherein the steel sheet further contains 0.01 to 0.2% of molybdenum. 49